CORE C. IMMUNE ASSAY, FLOW CYTOMETRY AND GENE PROFILING This Core will support the Projects of this program project by providing flow cytometry and gene expression profiling services and by performing in vitro functional assays to monitor the immune status of subjects participating in clinical trials. For the clinical trial described in Project 1, the Core will be used to document the development of T cell tolerance to donor or host alloantigens, and assess the ability of the reconstituted patients to mount an immune response to newly introduced as well as recall antigens. For all four Projects the Core will provide flow cytometry based cellular phenotype analysis including the determination of adequate host T cell depletion and the monitoring of T cell recovery following hematopoiefic progenitor cell transplantation for the patients in the clinical trials (Project 1) and for cell phenotype analysis and purification (Projects 2-4). The Core will also provide gene expression profiling to idenfify genes associated with clinical immune tolerance in transplant recipients (Project 1), identify specific cell types expressing these genes (Projects 1 and 4) or identify genes that are differentially expressed in functional subsets of dendritic cells (Project 4).